New Zealand was "reintegrated" into the controversial Five Eyes intelligence network only five years ago, America's top spy agency has revealed.

Responding to questions from Fairfax during Prime Minister John Key's trip to New York and Washington, the office of the Director of National Intelligence confirmed New Zealand was welcomed back into the fold in 2009 after a "2 decade absence".

Spokesman Brian Hale said reintegration happened after talks between our Five Eyes partners - the US, Australia, Canada and Britain - on the basis that it was believed to be "in the best interest of their nation and their group".

Prime Minister John Key said he could not recall any such change since National took office.

"I don't know exactly what they are referring to.

"My understanding of it is that even through the challenging times of the relationship post the anti-nuclear legislation, New Zealand continued to be an active member of Five Eyes."

Asked to confirm whether his Government had ever made a decision to actively rejoin Five Eyes, Key responded: "I don't think that's right, but I remember there were some vague things . . . "

He then said he would check.

"If they are increasingly sharing more, then that's news to me but they would know that more than I would."

Wikileaks documents previously obtained by Fairfax appear to confirm DNI's version of events, however, and suggest that former US Secretary of State Hillary Clinton had inadvertently announced a top secret deal on the resumption of intelligence sharing with New Zealand.

The leaked diplomatic cable warned Clinton not to acknowledge the position in public but she announced it at a joint press conference with Foreign Minister Murray McCully - an event which clearly caught New Zealand officials on the hop at the time.

Five Eyes is one of the most exclusive clubs in the world and refers to a five-nation intelligence sharing network which had its origins in World War II. The decades-old Waihopai spy station is the most visible symbol of New Zealand's membership.

Revelations by National Security Agency whistleblower Edward Snowden suggest it is part of a network that collects massive amounts of data about ordinary citizens and also spies on friendly governments.

That has sparked deep unease among many New Zealanders, as revealed by today's Stuff.co.nz/Ipsos poll, which shows a staggering 71.6 per cent of Kiwis believe United States spy agencies are gathering data on us.

The poll also reveals that 61.8 per cent of those people do not support the US being able to do so.

Key said how people responded to that question depended on the context. "If a New Zealander was training with a terrorist group in a foreign environment then it is possible that the US would gather information about that person because of their links to that terrorist organisation. I believe most New Zealanders would support that if the context of that question was asked.

"But if the question was: ‘Is the US spying on everyday New Zealanders in New Zealand?' then I would reject that proposition."

Hale said the National Security Agency's efforts were focused on "ensuring the protection of the national security of the United States, its citizens, and our allies through the pursuit of valid foreign intelligence targets only.

"Under the unique Five Eyes construct, each country contributes its insights and capabilities in return for access to the combined global resources of the other four partners."